Ahh good old Yoga Butt (to clarify—this is a term used when someone strains the area of their upper back thigh and the bottom of the butt – often times as a result of over stretching in yoga). It is a fairly common injury but not too difficult to heal with time.
If you have recently suffered from Yoga Butt the best thing to do is to keep away from workouts that encourage too much stretching such as Yoga, but also Pilates. Cardio is a great way to avoid irritating the hamstring attachment. Great options for this would be boxing and swimming (focusing on free style and back stroke). But not too worry, soon enough you can get back to all the savasanas you want!